His rankings rely on a combination of citation frequency and standardized citation rate (an attempt to measure impact by counting citations per article). Ronen makes this choice because he is interested in getting the incentives of law review editors right:

A continuous ranking according to citation frequency may encourage editors to publish more articles (or more extensive articles) of lesser value, and this in turn may reduce the average academic quality of each item. True, citation frequency is partly responsive to this possibility. Presumably, a legal periodical that publishes numerous articles of low quality will not be cited at all, whereas a legal periodical that publishes a few excellent articles will be cited quite often. So an uncontrolled increase of publication volume cannot be expected to result in a significant increase in citation frequency. Still, enlarging the publication volume increases a journal's likelihood of being cited as long as the additional text is not wholly inferior. Mediocre journals with high paginations may rank higher than excellent journals with low paginations. Editors will be led to publish more, and the average academic quality of law reviews might eventually drop.

A continuous ranking by standardized citation rates eliminates the incentive to publish more articles of lesser value, and thereby averts a decline in the average quality of legal periodicals. However, it might give editors an excessively strong incentive in the opposite direction. They may be encouraged to be more selective and publish less to ensure that their standardized citation rate is maximal. In the long run this might constrain and inhibit legal discourse.

He has a much more extensive discussion of the methodology in the paper, but I know that what you really want to see is the results. Here are the Top 25 general law reviews. See the paper if you want to see all 187, top to bottom.

One last point. Ronen examines the correlation between law review ranking and U.S. News and World Report ranking and finds a very high correlation: "The linear correlation coefficient between the school's ranking and its flagship law review's ranking is 0.8334." Not surprising, but again, the paper has a more extended discussion if you are interested.